This invention relates to the field of blowers. In particular, this invention is drawn to blower impeller designs.
Cabinetry or enclosures for heat generating equipment may contain one or more blowers for active or forced air cooling. The blower displaces the air within the enclosure volume with cooler air external to the enclosure volume. The blower acts as a pump to transfer air between the two environments. Depending upon the configuration, either the air within the enclosure or the air external to the enclosure is the source for the pump. Air pumped from the interior by the blower is replaced with air external to the enclosure through the vents. Alternatively, air pumped from the exterior of the enclosure into the enclosure displaces the air in the enclosure through the vents. Without active cooling, the components within the cabinetry can overheat resulting in erratic, unpredictable behavior or a shortened lifespan among other maladies.
Blower systems may incorporate multiple blowers for redundancy or to achieve a specific air flow pattern in order to ensure adequate cooling. The failure of a single blower, however, creates a new source for air. Moreover, the blower interface between the internal/external environments tends to be more efficient for transferring air than the enclosure vents. The blower interface thus tends to become a preferential source relative to the vents for the transfer of air. As a result, the air flow patterns within the enclosure may be sufficiently disrupted to prevent adequate cooling or to significantly decrease the efficiency of redundant blower systems.
One approach uses baffles to prevent reverse airflow. These baffles have a number of members that pivot to enable opening and closing the baffle. When the blower is off, gravity or other forces close the baffle. During normal operation, simple baffles rely upon the pressure developed by the blower to open. One disadvantage of simple baffles for equipment enclosures is the additional assembly steps required to mount the baffles on the equipment. Another disadvantage of simple baffles is that the baffles members significantly impeded the flow of air from the blower exhaust.
In view of limitations of known systems and methods, blower designs for vented enclosures are described. One blower design incorporates an impeller having a plurality of blades. The plurality of blades are pivotably coupled to an impeller body. Air flow between blades is substantially restricted when the blades are in a closed state. Air flow between the blades is permitted when the blades are in an open state. In one embodiment the pivotal couplings are spring loaded to maintain the blades in the closed state when the impeller rotational speed is below a threshold range.
One embodiment of a method for operating a blower includes the step of providing a blower having an impeller with pivotable blades. The blades are maintained in a closed state to restrict reverse air flow while an impeller rotational speed is below a threshold range. The blades are pivoted to an open state to permit air flow when an impeller rotational speed exceeds a threshold range.
In one embodiment, an apparatus includes an enclosure having at least one vent. The apparatus includes a plurality of blowers for exchanging air between the interior and the exterior of the enclosure in co-operation with the vent. Each blower comprises an impeller having pivotable blades. The pivotable blades pivot to permitting substantially no reverse air flow through the blower when the rotational speed of the impeller falls below a threshold range.
In various embodiments, the impellers are configured for centrifugal pumping action. For example, in various embodiments the impeller blades form one of an airfoil, backward inclined, backward curved, radial, paddle, and forward curved configuration.
Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below.